rationalist

UK: /ˈræʃ^ənəlɪst/

WordReference Random House Learner's Dictionary of American English © 2025

ra•tion•al•ism /ˈræʃənəlˌɪzəm/   n. [uncountable]

1. the principle or doctrine of using human reason as the basis for matters of opinion, belief, or conduct.
2. a doctrine in philosophy that stresses the use of reason as opposed to religious faith.

ra•tion•al•ist, n. [countable] See -ratio-.

WordReference Random House Unabridged Dictionary of American English © 2025

ra•tion•al•ism  (rash′ə nl iz′əm), n. 

1. the principle or habit of accepting reason as the supreme authority in matters of opinion, belief, or conduct.
2. Philosophy
   • the doctrine that reason alone is a source of knowledge and is independent of experience.
   • (in the philosophies of Descartes, Spinoza, etc.) the doctrine that all knowledge is expressible in self-evident propositions or their consequences.
3. Religion [Theol.] the doctrine that human reason, unaided by divine revelation, is an adequate or the sole guide to all attainable religious truth.
4. Architecture (often cap.)
   • a design movement principally of the mid-19th century that emphasized the development of modern ornament integrated with structure and the decorative use of materials and textures rather than as added adornment.
   • the doctrines and practices of this movement. Cf. functionalism (def. 1).

• rational + -ism 1790–1800

ra′tion•al•ist, n. 
ra′tion•al•is′tic, ra′tion•al•is′ti•cal, adj. 
ra′tion•al•is′ti•cal•ly, adv.